Reactive Extraction of Zn and Cu with Bis(2-Ethylhexyl)Phosphate: Optimization using Taguchi Orthogonal Design

Abstract

A comprehensive study on the reactive extraction of Zn and Cu has been established in an aqueous-organic two-phase system using bis(2-ethylhexyl)phosphate (HDEHP) to separate both the metals with the single extractant. Taguchi’s experimental design with orthogonal array L25 has been employed to evaluate the effect of most influencing parameters such as aqueous phase pH, carrier concentration, and contact time; experiments have been conducted accordingly. The optimum conditions have been obtained as following: aqueous phase pH 3.5 and 5.5 for Zn and Cu, respectively; carrier concentration, 15%; equilibrium time, 30 min. Under these optimum conditions, a quantitative extraction of Zn (91.8%) and Cu (90%) has been observed. Extraction equilibrium constant K_eq has been estimated as 3 × 10⁻³ (mol/L)^1/2 and 2.78 × 10⁻³ (mol/L)^−1/2 for Zn and Cu, respectively. Herein, a complementary kinetic study has been also performed and the extraction process has been found to conform to the chemical reaction controlled mechanism.